This proposal intends to eliminate the two most important impediments of the artificial heart as a bridge to donor heart transplantation in human patients today. The space problem is eliminated by introducing small artificial hearts that fit easily inside the human chest. Thromboemboli are prevented by eliminating their origin - mechanical valves and quick connectors, while replacing them by tissue valves which are directly sewn into atria, aorta and pulmonary artery. The blood contacting surface of the hearts will be covered with Dacron fibrils to prevent possible small thrombi to become emboli. Durability and functional performance of these new ventricles will be studied in the mock circulation. A new, all pneumatic drive system with low dp/dt will be used to drive the hearts. Physiological studies will provide data for optimal use of this combination. Pyrolysis Mass Spectroscopy (Biomaterials Profiling Center) and other techniques of the University of Utah will guarantee quality of materials and detect degeneration after use. Five sheep or calves per year will receive the new hearts. Our hypothesis is that blood damage and coagulopathy will be minimal: kidneys will be free of emboli; calcification will not occur within three months in sheep; and function will be adequate on treadmill exercise. Two brain dead human cadavers per year will receive the new hearts at Temple University. This will demonstrate that implantation without quick connectors does not increase bleeding, and that there is an easy fit because of small ventricle size and absence of quick connectors. Compromising large veins and atria is thus prevented. Physiological studies will show by temporarily reducing or increasing CO of one ventricle that Starling's Law applies to the function of the other ventricle of the artificial heart. Tricusp semilunar Polyurethane valves are under development. If satisfactory, they will gradually replace the tissue valves. The ventricles will also be used as L-RVAD's in calves. When successful, a chimeric donor heart will be implanted with the assist pump in situ, thus allowing the donor heart to recover from damage it may have incurred. When the animal has not thrown any emboli and when we recover the artificial ventricles anyway, we might as well give the animal a chance.